Electrically actuated X-Y shifting mechanisms for effecting change gear shifts in an automated mechanical transmissions are well known in the art. Such mechanisms typically include a plurality of substantially parallel, spaced-apart, axially movable shift rails each of which carry a shift fork which is associated with a positive clutch mechanism for selectively engaging or disengaging a first or second gear to a shaft. Typically shifting of the transmission is accomplished by selecting a shift rail by moving a shift finger axially or pivotally along an X--X axis into alignment with a shift block carried by the selected shift rail. Then the selected shift rail is axially moved to shift gears by axially moving or pivoting the shift finger to apply a force to the shift block in the direction of an axis Y--Y transverse to axis X--X. The shift finger is driven by electric motors, under the control of suitable electrical circuitry. See for example, U.S. Pat. No. 4,873,881 assigned to the assignee of the present invention, and hereby incorporated herein by reference. Such devices require calibration in order to insure that operation of the mechanism under software control produces accurate shifts. The calibration generally includes precise location of at least three rail positions and a neutral position. These positions are usually determined through a manual calibration procedure at the factory at the time of assembly which requires special equipment and detailed knowledge of the device. Moreover, temperature, component wear, and installation tolerances may cause the original calibration values to change over time. It is therefore desirable that these calibration values be updated periodically to insure optimal operation of the shifter.